#include <v8-profiler.h>

Data Structures
class	ObjectNameResolver

Public Types
enum	SamplingFlags { kSamplingNoFlags = 0, kSamplingForceGC = 1 << 0 }

typedef void(*	BuildEmbedderGraphCallback) (v8::Isolate isolate, v8::EmbedderGraph graph, void *data)

using	GetDetachednessCallback = EmbedderGraph::Node::Detachedness()(v8::Isolate isolate, const v8::Local< v8::Value > &v8_value, uint16_t class_id, void *data)

Public Member Functions
int	GetSnapshotCount ()

const HeapSnapshot *	GetHeapSnapshot (int index)

SnapshotObjectId	GetObjectId (Local< Value > value)

SnapshotObjectId	GetObjectId (NativeObject value)

Local< Value >	FindObjectById (SnapshotObjectId id)

void	ClearObjectIds ()

const HeapSnapshot *	TakeHeapSnapshot (ActivityControl control=nullptr, ObjectNameResolver global_object_name_resolver=nullptr, bool treat_global_objects_as_roots=true)

void	StartTrackingHeapObjects (bool track_allocations=false)

SnapshotObjectId	GetHeapStats (OutputStream stream, int64_t timestamp_us=nullptr)

void	StopTrackingHeapObjects ()

bool	StartSamplingHeapProfiler (uint64_t sample_interval=512 *1024, int stack_depth=16, SamplingFlags flags=kSamplingNoFlags)

void	StopSamplingHeapProfiler ()

AllocationProfile *	GetAllocationProfile ()

void	DeleteAllHeapSnapshots ()

void	AddBuildEmbedderGraphCallback (BuildEmbedderGraphCallback callback, void *data)

void	RemoveBuildEmbedderGraphCallback (BuildEmbedderGraphCallback callback, void *data)

void	SetGetDetachednessCallback (GetDetachednessCallback callback, void *data)

Static Public Attributes
static const SnapshotObjectId	kUnknownObjectId = 0

static const uint16_t	kPersistentHandleNoClassId = 0

Detailed Description

Interface for controlling heap profiling. Instance of the profiler can be retrieved using v8::Isolate::GetHeapProfiler.

Definition at line 815 of file v8-profiler.h.

Member Typedef Documentation

◆ BuildEmbedderGraphCallback

typedef void(* BuildEmbedderGraphCallback(v8::Isolate *isolate, v8::EmbedderGraph *graph, void *data)

Callback function invoked during heap snapshot generation to retrieve the embedder object graph. The callback should use graph->AddEdge(..) to add references between the objects. The callback must not trigger garbage collection in V8.

Definition at line 828 of file v8-profiler.h.

◆ GetDetachednessCallback

using GetDetachednessCallback = EmbedderGraph::Node::Detachedness (*)( v8::Isolate* isolate, const v8::Local<v8::Value>& v8_value, uint16_t class_id, void* data)

Callback function invoked during heap snapshot generation to retrieve the detachedness state of an object referenced by a TracedReference.

The callback takes Local<Value> as parameter to allow the embedder to unpack the TracedReference into a Local and reuse that Local for different purposes.

Definition at line 842 of file v8-profiler.h.

Member Enumeration Documentation

◆ SamplingFlags

enum SamplingFlags

Enumerator
kSamplingNoFlags
kSamplingForceGC

Definition at line 817 of file v8-profiler.h.

Member Function Documentation

◆ AddBuildEmbedderGraphCallback()

void AddBuildEmbedderGraphCallback	(	BuildEmbedderGraphCallback	callback,
		void *	data
	)

◆ ClearObjectIds()

void ClearObjectIds ( )

Clears internal map from SnapshotObjectId to heap object. The new objects will not be added into it unless a heap snapshot is taken or heap object tracking is kicked off.

◆ DeleteAllHeapSnapshots()

void DeleteAllHeapSnapshots ( )

Deletes all snapshots taken. All previously returned pointers to snapshots and their contents become invalid after this call.

◆ FindObjectById()

Local<Value> FindObjectById ( SnapshotObjectId id )

Returns heap object with given SnapshotObjectId if the object is alive, otherwise empty handle is returned.

◆ GetAllocationProfile()

AllocationProfile* GetAllocationProfile ( )

Returns the sampled profile of allocations allocated (and still live) since StartSamplingHeapProfiler was called. The ownership of the pointer is transferred to the caller. Returns nullptr if sampling heap profiler is not active.

◆ GetHeapSnapshot()

const HeapSnapshot* GetHeapSnapshot ( int index )

Returns a snapshot by index.

◆ GetHeapStats()

SnapshotObjectId GetHeapStats	(	OutputStream *	stream,
		int64_t *	timestamp_us = `nullptr`
	)

Adds a new time interval entry to the aggregated statistics array. The time interval entry contains information on the current heap objects population size. The method also updates aggregated statistics and reports updates for all previous time intervals via the OutputStream object. Updates on each time interval are provided as a stream of the HeapStatsUpdate structure instances. If |timestamp_us| is supplied, timestamp of the new entry will be written into it. The return value of the function is the last seen heap object Id.

StartTrackingHeapObjects must be called before the first call to this method.

◆ GetObjectId() [1/2]

SnapshotObjectId GetObjectId ( Local< Value > value )

Returns SnapshotObjectId for a heap object referenced by |value| if it has been seen by the heap profiler, kUnknownObjectId otherwise.

◆ GetObjectId() [2/2]

SnapshotObjectId GetObjectId ( NativeObject value )

Returns SnapshotObjectId for a native object referenced by |value| if it has been seen by the heap profiler, kUnknownObjectId otherwise.

◆ GetSnapshotCount()

int GetSnapshotCount ( )

Returns the number of snapshots taken.

◆ RemoveBuildEmbedderGraphCallback()

void RemoveBuildEmbedderGraphCallback	(	BuildEmbedderGraphCallback	callback,
		void *	data
	)

◆ SetGetDetachednessCallback()

void SetGetDetachednessCallback	(	GetDetachednessCallback	callback,
		void *	data
	)

◆ StartSamplingHeapProfiler()

bool StartSamplingHeapProfiler	(	uint64_t	sample_interval = `512 *1024`,
		int	stack_depth = `16`,
		SamplingFlags	flags = `kSamplingNoFlags`
	)

Starts gathering a sampling heap profile. A sampling heap profile is similar to tcmalloc's heap profiler and Go's mprof. It samples object allocations and builds an online 'sampling' heap profile. At any point in time, this profile is expected to be a representative sample of objects currently live in the system. Each sampled allocation includes the stack trace at the time of allocation, which makes this really useful for memory leak detection.

This mechanism is intended to be cheap enough that it can be used in production with minimal performance overhead.

Allocations are sampled using a randomized Poisson process. On average, one allocation will be sampled every |sample_interval| bytes allocated. The |stack_depth| parameter controls the maximum number of stack frames to be captured on each allocation.

NOTE: This is a proof-of-concept at this point. Right now we only sample newspace allocations. Support for paged space allocation (e.g. pre-tenured objects, large objects, code objects, etc.) and native allocations doesn't exist yet, but is anticipated in the future.

Objects allocated before the sampling is started will not be included in the profile.

Returns false if a sampling heap profiler is already running.

◆ StartTrackingHeapObjects()

void StartTrackingHeapObjects ( bool track_allocations = false )

Starts tracking of heap objects population statistics. After calling this method, all heap objects relocations done by the garbage collector are being registered.

|track_allocations| parameter controls whether stack trace of each allocation in the heap will be recorded and reported as part of HeapSnapshot.

◆ StopSamplingHeapProfiler()

void StopSamplingHeapProfiler ( )

Stops the sampling heap profile and discards the current profile.

◆ StopTrackingHeapObjects()

void StopTrackingHeapObjects ( )

Stops tracking of heap objects population statistics, cleans up all collected data. StartHeapObjectsTracking must be called again prior to calling GetHeapStats next time.

◆ TakeHeapSnapshot()

const HeapSnapshot* TakeHeapSnapshot	(	ActivityControl *	control = `nullptr`,
		ObjectNameResolver *	global_object_name_resolver = `nullptr`,
		bool	treat_global_objects_as_roots = `true`
	)

Takes a heap snapshot and returns it.

Field Documentation

◆ kPersistentHandleNoClassId

const uint16_t kPersistentHandleNoClassId = 0

static

Default value of persistent handle class ID. Must not be used to define a class. Can be used to reset a class of a persistent handle.

Definition at line 1001 of file v8-profiler.h.

◆ kUnknownObjectId

const SnapshotObjectId kUnknownObjectId = 0